提交 8a966ed7 编写于 作者: E Ebru Akagunduz 提交者: Linus Torvalds

mm: make swapin readahead to improve thp collapse rate

This patch makes swapin readahead to improve thp collapse rate.  When
khugepaged scanned pages, there can be a few of the pages in swap area.

With the patch THP can collapse 4kB pages into a THP when there are up
to max_ptes_swap swap ptes in a 2MB range.

The patch was tested with a test program that allocates 400B of memory,
writes to it, and then sleeps.  I force the system to swap out all.
Afterwards, the test program touches the area by writing, it skips a
page in each 20 pages of the area.

Without the patch, system did not swap in readahead.  THP rate was %65
of the program of the memory, it did not change over time.

With this patch, after 10 minutes of waiting khugepaged had collapsed
%99 of the program's memory.

[kirill.shutemov@linux.intel.com: trivial cleanup of exit path of the function]
[kirill.shutemov@linux.intel.com: __collapse_huge_page_swapin(): drop unused 'pte' parameter]
[kirill.shutemov@linux.intel.com: do not hold anon_vma lock during swap in]
Signed-off-by: NEbru Akagunduz <ebru.akagunduz@gmail.com>
Acked-by: NRik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Xie XiuQi <xiexiuqi@huawei.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
上级 70652f6e
......@@ -135,5 +135,29 @@ TRACE_EVENT(mm_collapse_huge_page_isolate,
__print_symbolic(__entry->status, SCAN_STATUS))
);
TRACE_EVENT(mm_collapse_huge_page_swapin,
TP_PROTO(struct mm_struct *mm, int swapped_in, int ret),
TP_ARGS(mm, swapped_in, ret),
TP_STRUCT__entry(
__field(struct mm_struct *, mm)
__field(int, swapped_in)
__field(int, ret)
),
TP_fast_assign(
__entry->mm = mm;
__entry->swapped_in = swapped_in;
__entry->ret = ret;
),
TP_printk("mm=%p, swapped_in=%d, ret=%d",
__entry->mm,
__entry->swapped_in,
__entry->ret)
);
#endif /* __HUGE_MEMORY_H */
#include <trace/define_trace.h>
......@@ -2373,6 +2373,44 @@ static bool hugepage_vma_check(struct vm_area_struct *vma)
return !(vma->vm_flags & VM_NO_THP);
}
/*
* Bring missing pages in from swap, to complete THP collapse.
* Only done if khugepaged_scan_pmd believes it is worthwhile.
*
* Called and returns without pte mapped or spinlocks held,
* but with mmap_sem held to protect against vma changes.
*/
static void __collapse_huge_page_swapin(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd)
{
unsigned long _address;
pte_t *pte, pteval;
int swapped_in = 0, ret = 0;
pte = pte_offset_map(pmd, address);
for (_address = address; _address < address + HPAGE_PMD_NR*PAGE_SIZE;
pte++, _address += PAGE_SIZE) {
pteval = *pte;
if (!is_swap_pte(pteval))
continue;
swapped_in++;
ret = do_swap_page(mm, vma, _address, pte, pmd,
FAULT_FLAG_ALLOW_RETRY|FAULT_FLAG_RETRY_NOWAIT,
pteval);
if (ret & VM_FAULT_ERROR) {
trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0);
return;
}
/* pte is unmapped now, we need to map it */
pte = pte_offset_map(pmd, _address);
}
pte--;
pte_unmap(pte);
trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1);
}
static void collapse_huge_page(struct mm_struct *mm,
unsigned long address,
struct page **hpage,
......@@ -2440,6 +2478,8 @@ static void collapse_huge_page(struct mm_struct *mm,
goto out;
}
__collapse_huge_page_swapin(mm, vma, address, pmd);
anon_vma_lock_write(vma->anon_vma);
pte = pte_offset_map(pmd, address);
......@@ -2516,9 +2556,6 @@ static void collapse_huge_page(struct mm_struct *mm,
result = SCAN_SUCCEED;
out_up_write:
up_write(&mm->mmap_sem);
trace_mm_collapse_huge_page(mm, isolated, result);
return;
out_nolock:
trace_mm_collapse_huge_page(mm, isolated, result);
return;
......
......@@ -36,6 +36,10 @@
/* Do not use these with a slab allocator */
#define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
extern int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
unsigned int flags, pte_t orig_pte);
void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
unsigned long floor, unsigned long ceiling);
......
......@@ -2522,7 +2522,7 @@ EXPORT_SYMBOL(unmap_mapping_range);
* We return with the mmap_sem locked or unlocked in the same cases
* as does filemap_fault().
*/
static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
unsigned int flags, pte_t orig_pte)
{
......
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